Dies including strain gauge sensors and temperature sensors

ABSTRACT

A die includes a plurality of fluid actuation devices and at least one strain gauge sensor to sense strain. The die also includes at least one temperature sensor to sense the temperature of the die to compensate for a temperature component of the sensed strain.

BACKGROUND

An inkjet printing system, as one example of a fluid ejection system,may include a printhead, an ink supply which supplies liquid ink to theprinthead, and an electronic controller which controls the printhead.The printhead, as one example of a fluid ejection device, ejects dropsof ink through a plurality of nozzles or orifices and toward a printmedium, such as a sheet of paper, so as to print onto the print medium.In some examples, the orifices are arranged in at least one column orarray such that properly sequenced ejection of ink from the orificescauses characters or other images to be printed upon the print medium asthe printhead and the print medium are moved relative to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram illustrating one example of a die.

FIG. 1B is a block diagram illustrating one example of a fluid ejectionsystem.

FIG. 1C is a block diagram illustrating another example of a fluidejection system.

FIG. 2A illustrates one example of a strain gauge sensor.

FIG. 2B illustrates another example of a strain gauge sensor.

FIG. 3A illustrates one example of a strain gauge sensor co-located witha temperature sensor.

FIG. 3B illustrates one example of a strain gauge sensor used to sensetemperature.

FIG. 4A illustrates one example of the output of a strain gauge sensorwith no change in temperature.

FIG. 4B illustrates one example of the output of a strain gauge sensorwith varying temperature.

FIG. 4C illustrates one example of the output of a temperature sensor.

FIG. 4D illustrates one example of the temperature compensated output ofa strain gauge sensor.

FIG. 5 illustrates a front view of one example of a fluid ejection die.

FIG. 6 illustrates a front view of another example of a fluid ejectiondie.

FIG. 7 is a flow diagram illustrating one example of a method formaintaining a fluid ejection system.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific examples in which the disclosure may bepracticed. It is to be understood that other examples may be utilizedand structural or logical changes may be made without departing from thescope of the present disclosure. The following detailed description,therefore, is not to be taken in a limiting sense, and the scope of thepresent disclosure is defined by the appended claims. It is to beunderstood that features of the various examples described herein may becombined, in part or whole, with each other, unless specifically notedotherwise.

It is desirable to be able to determine the strain at points on asemiconductor die, such as a die including fluid actuation devices(e.g., a fluid ejection die), in the presence of a varying temperature.A varying temperature, however, may affect the output from strain gaugesensors. Accordingly, described herein is a die including at least onestrain gauge sensor integrated within the die. The at least one straingauge sensor senses the strain within the die at the location of the atleast one strain gauge sensor. The die also includes at least onetemperature sensor to sense the temperature of the die at the locationof the at least one strain gauge sensor. The temperature at the at leastone strain gauge sensor may be sensed directly by a temperature sensoror interpolated from a plurality of sensed temperatures from a pluralityof temperature sensors. The sensed temperature is used to compensate fora temperature component of the sensed strain.

FIG. 1A is a block diagram illustrating one example of a die 10. Die 10includes a plurality of fluid actuation devices 12, at least one straingauge sensor 14 to sense strain, and at least one temperature sensor 16.The at least one temperature sensor 16 senses the temperature of die 10to compensate for a temperature component of the sensed strain. In oneexample, the at least one strain gauge sensor 14 includes apiezoresistive sensor element, as will be described in detail below withreference to FIG. 2A. In another example, the at least one strain gaugesensor 14 includes three piezoresistive sensor elements in a rosetteconfiguration, as will be described in detail below with reference toFIG. 2B.

In one example, the at least one temperature sensor 16 includes a diode,a thermistor, a thermocouple, a silicon bandgap temperature sensor, oranother suitable temperature sensor. In another example, the at leastone temperature sensor 16 may include a further strain gauge sensor. Thefurther strain gauge sensor 16 may include four piezoresistive sensorelements in a Wheatstone bridge configuration (as will be described indetail below with reference to FIG. 3B) co-located with the at least onestrain gauge sensor 14. In this case, the sensed temperature is based onthe difference in the sensed strain between the at least one straingauge sensor 14 and the further strain gauge sensor 16.

In another example, the at least one temperature sensor 16 includes afurther strain gauge sensor including three piezoresistive sensorelements in a rosette configuration at a location of the fluid ejectiondie having substantially no stress. Since the output of the furtherstrain gauge sensor 16 is not affected by stress, the output of thefurther strain gauge sensor 16 provides an indication of temperature.Accordingly, in this case, the sensed temperature is based on thedifference in the sensed strain between the at least one strain gaugesensor 14 and the further strain gauge sensor 16.

FIG. 1B is a block diagram illustrating one example of a fluid ejectionsystem 20. Fluid ejection system 20 includes a fluid ejection die 21 anda controller 30. Fluid ejection die 21 is electrically coupled tocontroller 30 through a signal path 28. Fluid ejection die 21 includes aplurality of actuation devices 22 to eject fluid drops. In one example,actuation devices 22 are nozzles or fluidic pumps to eject fluid drops.Fluid ejection die 21 also includes a plurality of strain gauge sensors24 to sense strain within the fluid ejection die 21 and a plurality oftemperature sensors 26 to sense temperature within the fluid ejectiondie 21. Controller 30 receives the sensed strain from each strain gaugesensor 24 and the sensed temperature from each temperature sensor 26 andprovides a temperature compensated strain for each sensed strain basedon the sensed temperatures.

FIG. 1C is a block diagram illustrating another example of a fluidejection system 100. Fluid ejection system 100 includes a fluid ejectionassembly, such as printhead assembly 102, and a fluid supply assembly,such as ink supply assembly 110. In the illustrated example, fluidejection system 100 also includes a service station assembly 104, acarriage assembly 116, a print media transport assembly 118, and anelectronic controller 120. While the following description providesexamples of systems and assemblies for fluid handling with regard toink, the disclosed systems and assemblies are also applicable to thehandling of fluids other than ink.

Printhead assembly 102 includes at least one printhead or fluid ejectiondie 106 which ejects drops of ink or fluid through a plurality oforifices or nozzles 108. In one example, the drops are directed toward amedium, such as print media 124, so as to print onto print media 124. Inone example, print media 124 includes any type of suitable sheetmaterial, such as paper, card stock, transparencies, Mylar, fabric, andthe like. In another example, print media 124 includes media forthree-dimensional (3D) printing, such as a powder bed, or media forbioprinting and/or drug discovery testing, such as a reservoir orcontainer. In one example, nozzles 108 are arranged in at least onecolumn or array such that properly sequenced ejection of ink fromnozzles 108 causes characters, symbols, and/or other graphics or imagesto be printed upon print media 124 as printhead assembly 102 and printmedia 124 are moved relative to each other.

Fluid ejection die 106 also includes a plurality of strain gauge sensors107 and a plurality of temperature sensors 109. The strain gauge sensors107 sense strain within fluid ejection die 106. In one example, straingauge sensors 107 enable fluid ejection system 100 to monitor the stressexperienced by fluid ejection die 106. Each strain gauge sensor 107exhibits changes in electrical conductivity when corresponding areas offluid ejection die 106 are stressed. The amount of stress is quantifiedby measuring the changes in conductivity. By analyzing the stress ateach corresponding area of fluid ejection die 106, numerous diagnosticsmay be performed. The temperature sensors 109 sense the temperaturewithin fluid ejection die 106 at the locations of strain gauge sensors107. The sensed temperatures are used to compensate for a temperaturecomponent of each sensed strain.

Ink supply assembly 110 supplies ink to printhead assembly 102 andincludes a reservoir 112 for storing ink. As such, in one example, inkflows from reservoir 112 to printhead assembly 102. In one example,printhead assembly 102 and ink supply assembly 110 are housed togetherin an inkjet or fluid-jet print cartridge or pen. In another example,ink supply assembly 110 is separate from printhead assembly 102 andsupplies ink to printhead assembly 102 through an interface connection113, such as a supply tube and/or valve.

Carriage assembly 116 positions printhead assembly 102 relative to printmedia transport assembly 118, and print media transport assembly 118positions print media 124 relative to printhead assembly 102. Thus, aprint zone 126 is defined adjacent to nozzles 108 in an area betweenprinthead assembly 102 and print media 124. In one example, printheadassembly 102 is a scanning type printhead assembly such that carriageassembly 116 moves printhead assembly 102 relative to print mediatransport assembly 118. In another example, printhead assembly 102 is anon-scanning type printhead assembly such that carriage assembly 116fixes printhead assembly 102 at a prescribed position relative to printmedia transport assembly 118.

Service station assembly 104 provides for spitting, wiping, capping,and/or priming of printhead assembly 102 to maintain the functionalityof printhead assembly 102 and, more specifically, nozzles 108. Forexample, service station assembly 104 may include a rubber blade orwiper which is periodically passed over printhead assembly 102 to wipeand clean nozzles 108 of excess ink. In addition, service stationassembly 104 may include a cap that covers printhead assembly 102 toprotect nozzles 108 from drying out during periods of non-use. Inaddition, service station assembly 104 may include a spittoon into whichprinthead assembly 102 ejects ink during spits to insure that reservoir112 maintains an appropriate level of pressure and fluidity, and toinsure that nozzles 108 do not clog or weep. Functions of servicestation assembly 104 may include relative motion between service stationassembly 104 and printhead assembly 102.

Electronic controller 120 communicates with printhead assembly 102through a communication path 103, service station assembly 104 through acommunication path 105, carriage assembly 116 through a communicationpath 117, and print media transport assembly 118 through a communicationpath 119. In one example, when printhead assembly 102 is mounted incarriage assembly 116, electronic controller 120 and printhead assembly102 may communicate via carriage assembly 116 through a communicationpath 101. Electronic controller 120 may also communicate with ink supplyassembly 110 such that, in one implementation, a new (or used) inksupply may be detected.

Electronic controller 120 receives data 128 from a host system, such asa computer, and may include memory for temporarily storing data 128.Data 128 may be sent to fluid ejection system 100 along an electronic,infrared, optical or other information transfer path. Data 128represent, for example, a document and/or file to be printed. As such,data 128 form a print job for fluid ejection system 100 and includes atleast one print job command and/or command parameter.

In one example, electronic controller 120 provides control of printheadassembly 102 including timing control for ejection of ink drops fromnozzles 108. As such, electronic controller 120 defines a pattern ofejected ink drops which form characters, symbols, and/or other graphicsor images on print media 124. Timing control and, therefore, the patternof ejected ink drops, is determined by the print job commands and/orcommand parameters. In one example, logic and drive circuitry forming aportion of electronic controller 120 is located on printhead assembly102. In another example, logic and drive circuitry forming a portion ofelectronic controller 120 is located off printhead assembly 102.

Electronic controller 120 also receives the sensed strain from each ofthe plurality of strain gauge sensors 107 and the sensed temperaturefrom each of the plurality of temperature sensors 109 to determine thetemperature compensated strain at various locations within fluidejection die 106. Electronic controller 120 may use the temperaturecompensated strain at the various locations within fluid ejection die106 for numerous purposes, such as to control operations of fluidejection system 100 or to alert a user of fluid ejection system 100about the status of fluid ejection die 106.

FIG. 2A illustrates one example of a strain gauge sensor 200. In oneexample, strain gauge sensor 200 provides strain gauge sensor 14 of die10 previously described and illustrated with reference to FIG. 1A, eachstrain gauge sensor 24 of fluid ejection die 21 previously described andillustrated with reference to FIG. 1B, or each strain gauge sensor 107of fluid ejection die 106 previously described and illustrated withreference to FIG. 1C. Strain gauge sensor 200 includes a first electrode202, a second electrode 204, and a piezoresistive sensor element 206electrically coupled between first electrode 202 and second electrode204. Piezoresistive sensor element 206 exhibits a change in resistancein response to stress in one axis. Therefore, by biasing strain gaugesensor 200 with a constant current and measuring the voltage acrosspiezoresistive sensor element 206 or by biasing strain gauge sensor 200with a constant voltage and measuring the current through piezoresistivesensor element 206, the strain on piezoresistive sensor element 206 maybe sensed.

FIG. 2B illustrates another example of a strain gauge sensor 220. In oneexample, strain gauge sensor 220 provides strain gauge sensor 14 of die10 previously described and illustrated with reference to FIG. 1A, eachstrain gauge sensor 24 of fluid ejection die 21 previously described andillustrated with reference to FIG. 1B, or each strain gauge sensor 107of fluid ejection die 106 previously described and illustrated withreference to FIG. 1C. Strain gauge sensor 220 includes a first electrode222, a second electrode 224, and a first piezoresistive sensor element226 electrically coupled between first electrode 222 and secondelectrode 224. Strain gauge sensor 220 also includes a third electrode228, a fourth electrode 230, and a second piezoresistive sensor element232 electrically coupled between third electrode 228 and fourthelectrode 230. Strain gauge sensor 220 also includes a fifth electrode234, a sixth electrode 236, and a third piezoresistive sensor element238 electrically coupled between fifth electrode 234 and sixth electrode236.

Strain gauge sensor 220 exhibits a change in resistance in response tostress in three directions (e.g., X, Y, and XY). Strain gauge sensor 220is configured in a rosette configuration. Accordingly, by biasing eachpiezoresistive sensor element 226, 232, and 238 with a constant currentand measuring the voltage across each piezoresistive sensor element 226,232, and 238, respectively, or by biasing each piezoresistive sensorelement 226, 232, and 238 with a constant voltage and measuring thecurrent through each piezoresistive sensor element 226, 232, and 238,respectively, the strain on strain gauge sensor 220 may be sensed.

FIG. 3A illustrates one example of a strain gauge sensor 220 co-locatedwith a temperature sensor 302. In one example, temperature sensor 302provides temperature sensor 16 previously described and illustrated withreference to FIG. 1A, each temperature sensor 26 previously describedand illustrated with reference to FIG. 1B, or each temperature sensor109 previously described and illustrated with reference to FIG. 1C.Strain gauge sensor 220 was previously described above with reference toFIG. 2B. In this example, temperature sensor 302 is co-located withstrain gauge sensor 220 adjacent to first electrode 222, third electrode228, and fifth electrode 234. Temperature sensor 302 may be athermistor, a thermocouple, a silicon bandgap temperature sensor, oranother suitable temperature sensor.

FIG. 3B illustrates one example of a strain gauge sensor 320 used tosense temperature. In one example, strain gauge sensor 320 providestemperature sensor 16 previously described and illustrated withreference to FIG. 1A, each temperature sensor 26 previously describedand illustrated with reference to FIG. 1B, or each temperature sensor109 previously described and illustrated with reference to FIG. 1C.Strain gauge sensor 320 includes a first electrode 322, a secondelectrode 324, a third electrode 326, a fourth electrode 328, a firstpiezoresistive sensor element 330, a second piezoresistive sensorelement 331, a third piezoresistive sensor element 332, and a fourthpiezoresistive sensor element 333. First piezoresistive sensor element330 is electrically coupled between first electrode 322 and secondelectrode 324. Second piezoresistive sensor element 331 is electricallycoupled between second electrode 324 and third electrode 326. Thirdpiezoresistive sensor element 332 is electrically coupled between thirdelectrode 326 and fourth electrode 328. Fourth piezoresistive sensorelement 333 is electrically coupled between fourth electrode 328 andfirst electrode 322.

Strain gauge sensor 320 exhibits a change in resistance in response tostress in two axes. Strain gauge sensor 320 is configured in aWheatstone bridge configuration in which an external biasing voltage isapplied across two opposing electrodes (e.g., first electrode 322 andthird electrode 326) while the voltage is measured across the other twoopposing electrodes (e.g., second electrode 324 and fourth electrode328). The Wheatstone bridge configuration is inherently temperaturecompensated. Therefore, by biasing strain gauge sensor 320 with anexternal voltage and measuring the voltage across piezoresistive sensorelements 330-333, the inherently temperature compensated strain onstrain gauge sensor 320 may be sensed. The difference in the sensedstain between strain gauge sensor 320 and a non-inherently temperaturecompensated strain gauge sensor, such as strain gauge sensor 220previously described and illustrated with reference to FIG. 2B, is usedto determine the sensed temperature. The sensed temperature may then beused to compensate for the temperature component of the sensed strainfrom strain gauge sensor 220. This may be advantageous since the rosetteconfiguration of strain gauge sensor 220 provides more information aboutstress direction than the Wheatstone bridge configuration of straingauge sensor 320.

FIG. 4A illustrates one example of the output 400 of a strain gaugesensor with no change in temperature. In this example, the sensor output400 is in response to the presence of an oscillating source of stress(e.g., a print carriage moving a printhead back and forth) with nochange in temperature. FIG. 4B illustrates one example of the output 402of a strain gauge sensor with varying temperature. In this example, thesensor output 402 is from the same strain gauge sensor as in FIG. 4A,but in the presence of a steep temperature change (e.g., warming as aresult of printing or warming in preparation for printing). The sensedstress is overwhelmed by the change in temperature, providing anunusable signal. FIG. 4C illustrates one example of the output 404 of atemperature sensor. The temperature sensor is co-located with the straingauge sensor providing the output signal 402 of FIG. 4B. This signal isfree of strain information. FIG. 4D illustrates one example of thetemperature compensated output 406 of a strain gauge sensor. Thetemperature compensated output 406 includes the stress information fromoutput signal 402 of FIG. 4B with the temperature component from thetemperature sensor output 404 of FIG. 4C removed from the signal.

FIG. 5 illustrates a front view of one example of a fluid ejection die500. In one example, fluid ejection die 500 provides fluid ejection die21 previously described and illustrated with reference to FIG. 1B orfluid ejection die 106 previously described and illustrated withreference to FIG. 1C. Fluid ejection die 500 includes a plurality ofstrain gauge sensors co-located with a corresponding plurality oftemperatures sensors as indicated by 504. In this example, each filledbox of 504 indicates a strain gauge sensor and each empty box of 504indicates a temperature sensor. Fluid ejection die 500 also includes aplurality of bond pads 506 and a plurality of slots 508. Each slot 508delivers fluid to a plurality of corresponding nozzles (not shown)adjacent to each slot 508. In one example, fluid ejection die 500 is asilicon die and each of the plurality of strain gauge sensors andco-located temperature sensors 504 are integrated within the die. Eachstrain gauge sensor senses the strain within fluid ejection die 500 at aunique location within fluid ejection die 500, and each temperaturesensor senses the temperature within fluid ejection die 500 at thecorresponding location of each strain gauge sensor.

A plurality of strain gauge sensors and co-located temperature sensors504 may be arranged in at least one column (e.g., three in this example)parallel to slots 508. In this example, one column of strain gaugesensors and co-located temperature sensors 504 are arranged betweenslots 508 in the center of fluid ejection die 500, and two columns ofstrain gauge sensors and co-located temperature sensors 504 are arrangedon opposing sides of fluid ejection die 500. Strain gauge sensors andco-located temperature sensors 504 distributed throughout fluid ejectiondie 500 may be used to determine a temperature compensated strainprofile or stress signature across fluid ejection die 500.

Slots 508 are arranged along the length of fluid ejection die 500between bond pads 506. A first plurality of strain gauge sensors andco-located temperature sensors 504 surround a first end of each slot508, and a second plurality of strain gauge sensors and co-locatedtemperature sensors 504 surround a second end of each slot 508. In thisexample, five strain gauge sensors and co-located temperature sensors504 surround each end of each slot 508. The ends of slots 508 are highstress regions within fluid ejection die 500 due to the silicon slottingprocess used to form the slots. The strain gauge sensors and co-locatedtemperature sensors 504 surrounding the ends of each slot 508 monitorthese regions to determine the status of fluid ejection die 500.

Bond pads 506 are arranged on a first end of fluid ejection die 500 andon a second end of fluid ejection die 500 opposite to the first end. Inanother example, bond pads 506 are also arranged on the side of fluidejection die 500 instead of or in addition to the top of fluid ejectiondie 500. Bond pads 506 electrically couple fluid ejection die 500 to afluid ejection system when fluid ejection die 500 is installed in thesystem. A plurality of strain gauge sensors and co-located temperaturesensors 504 are proximate bond pads 506. In this example, six straingauge sensors and co-located temperature sensors 504 are proximate bondpads 506 (i.e., three strain gauge sensors and co-located temperaturesensors 504 proximate bond pads 506 on the first end of fluid ejectiondie 500 and three strain gauge sensors and co-located temperaturesensors 504 proximate bond pads 506 on the second end of fluid ejectiondie 500). Bond pads 506 are high stress regions within fluid ejectiondie 500 due to electrical interconnects, bond pad encapsulants, and bondpad adhesives. The strain gauge sensors and co-located temperaturesensors 504 proximate the bond pads 506 monitor these regions todetermine the status of fluid ejection die 500. In other examples,strain gauge sensors and co-located temperature sensors 504 may bearranged at various other locations within fluid ejection die 500.

FIG. 6 illustrates a front view of another example of a fluid ejectiondie 600. Fluid ejection die 600 is similar to fluid ejection die 500previously described and illustrated with reference to FIG. 5 exceptthat in fluid ejection die 600 some strain gauge sensors and co-locatedtemperature sensors 504 are replaced with strain gauge sensors 604,which do not include a co-located temperature sensor. In this example,fluid ejection die 600 includes more strain gauge sensors thantemperature sensors. Within each column of strain gauge sensors, everyother strain gauge sensor includes a co-located temperature sensor. Onetemperature sensor is arranged at each end of each slot 508. In thiscase, the sensed strain from each strain gauge sensor may be temperaturecompensated by using the temperature sensed from the co-locatedtemperature sensor if present (e.g., for strain gauge sensors withco-located temperature sensors 504), from the nearest temperature sensor(e.g., for the strain gauge sensors 604 at the ends of each slot 508),or by interpolating the temperature at the location of the strain gaugesensor based on the sensed temperatures from at least two temperaturesensors (e.g., for the strain gauge sensors 604 arranged in thecolumns).

FIG. 7 is a flow diagram illustrating one example of a method 700 formaintaining a fluid ejection system. At 702, method 700 includes sensingthe strain at a plurality of locations within a fluid ejection die viastrain gauge sensors integrated within the fluid ejection die. In oneexample, sensing the strain includes sensing the strain in threedirections at each of the plurality of locations. At 704, method 700includes sensing the temperature at the plurality of locations withinthe fluid ejection die via temperature sensors integrated within thefluid ejection die. In one example, sensing the temperature includessensing the temperature at each location within the fluid ejection dievia a temperature sensor corresponding to each strain gauge sensor.Method 700 may also include interpolating the temperature at a portionof the plurality of locations based on sensed temperatures from at leasttwo temperature sensors. At 706, method 700 includes compensating thesensed strain from each strain gauge sensor based on the sensedtemperatures.

Although specific examples have been illustrated and described herein, avariety of alternate and/or equivalent implementations may besubstituted for the specific examples shown and described withoutdeparting from the scope of the present disclosure. This application isintended to cover any adaptations or variations of the specific examplesdiscussed herein. Therefore, it is intended that this disclosure belimited only by the claims and the equivalents thereof.

The invention claimed is:
 1. A die comprising: a plurality of fluidactuation devices; at least one strain gauge sensor to sense a strainwithin the die; and at least one temperature sensor to sense thetemperature of the die to compensate for a temperature component of thesensed strain.
 2. The die of claim 1, wherein the at least one straingauge sensor comprises a piezoresistive sensor element.
 3. The die ofclaim 1, wherein the at least one strain gauge sensor comprises threepiezoresistive sensor elements in a rosette configuration.
 4. The die ofclaim 1, wherein the at least one temperature sensor comprises a furtherstrain gauge sensor.
 5. The die of claim 4, wherein the further straingauge sensor comprises four piezoresistive sensor elements in aWheatstone bridge configuration co-located with the at least one straingauge sensor, and wherein the sensed temperature is based on thedifference in the sensed strain between the at least one strain gaugesensor and the further strain gauge sensor.
 6. The die of claim 4,wherein the at least one temperature sensor comprises threepiezoresistive sensor elements in a rosette configuration at a locationof the fluid ejection die having substantially no stress.
 7. A fluidejection system comprising: a fluid ejection die comprising a pluralityof actuation devices to eject fluid drops, a plurality of strain gaugesensors to sense a strain within the fluid ejection die, and a pluralityof temperature sensors to sense temperature within the fluid ejectiondie; and a controller to receive the sensed strain from each straingauge sensor and the sensed temperature from each temperature sensor andprovide a temperature compensated strain for each sensed strain based onthe sensed temperatures.
 8. The fluid ejection system of claim 7,wherein each strain gauge sensor comprises three piezoresistive sensorelements in a rosette configuration.
 9. The fluid ejection system ofclaim 7, wherein the fluid ejection die comprises one temperature sensorfor each strain gauge sensor.
 10. The fluid ejection system of claim 7,wherein the fluid ejection die comprises more strain gauge sensors thantemperature sensors.
 11. The fluid ejection system of claim 7, whereineach strain gauge sensor is co-located with a temperature sensor.
 12. Amethod for maintaining a fluid ejection system, the method comprising:sensing a strain at a plurality of locations within a fluid ejection dievia strain gauge sensors integrated within the fluid ejection die;sensing the temperature at the plurality of locations within the fluidejection die via temperature sensors integrated within the fluidejection die; and compensating the sensed strain from each strain gaugesensor based on the sensed temperatures.
 13. The method of claim 12,wherein sensing the strain comprises sensing the strain in threedirections at each of the plurality of locations.
 14. The method ofclaim 12, wherein sensing the temperature comprises sensing thetemperature at each location within the fluid ejection die via atemperature sensor corresponding to each strain gauge sensor.
 15. Themethod of claim 12, further comprising: interpolating the temperature ata portion of the plurality of locations based on sensed temperaturesfrom at least two temperature sensors.